Skin tags form when your body produces extra cells in the top layers of skin, usually in areas where skin rubs against itself. They’re one of the most common benign skin growths in adults, and while they’re harmless, the reasons behind them go deeper than simple friction. A combination of mechanical irritation, hormonal signals, metabolic factors, and genetics all play a role.
What a Skin Tag Actually Is
A skin tag is a small, soft pouch of tissue that hangs off your skin by a thin stalk. Inside, it contains fat, collagen fibers, and sometimes nerve cells and small blood vessels. The leading theory is that these collagen fibers and blood vessels get wrapped up inside a layer of skin, forming the characteristic bump. Most are tiny, just a few millimeters, though some grow to a centimeter or more.
They show up most often in skin folds and areas of repeated movement: the neck, armpits, under the breasts, groin, and eyelids. These are all spots where skin slides against skin or clothing throughout the day, which is a major clue to one of the primary causes.
Friction Triggers Growth
Repeated rubbing is the most straightforward explanation for many skin tags. When skin constantly folds and rubs against itself, the irritation can stimulate the top layers of skin to overproduce cells. That’s why skin tags cluster in creases and folds rather than on flat, exposed areas like your forearms or shins. Clothing that chafes, jewelry like necklaces, and even seatbelts can create the same effect in specific spots.
This also explains why people who carry more body weight tend to develop more skin tags. More skin folds mean more surface area where friction occurs throughout the day.
Insulin Resistance and Metabolism
Friction isn’t the whole story. There’s a strong metabolic component, and it centers on insulin. When your body becomes resistant to insulin (a precursor to type 2 diabetes), it compensates by producing more of it. That excess insulin activates growth factor receptors on skin cells called fibroblasts and keratinocytes, essentially telling them to multiply faster than normal. The result is extra tissue growth, including skin tags.
Research has found significant correlations between skin tag count and several metabolic markers: BMI, blood sugar levels, hemoglobin A1c (a measure of long-term blood sugar control), cholesterol, and LDL levels. In fact, skin tags are now considered a cutaneous marker for these metabolic risk factors. If you’re developing multiple skin tags, particularly in clusters, it can be an outward signal that your blood sugar or insulin levels deserve a closer look.
People with obesity may be especially prone because of a combination of factors working together: increased friction from skin folds, insulin resistance, higher circulating insulin, and elevated levels of leptin, a hormone involved in appetite and energy balance.
Hormonal Changes
Pregnancy is a well-known trigger. Many women notice new skin tags appearing during pregnancy, likely driven by the surge in growth hormones and other hormonal shifts that occur. Hormones in birth control pills can produce similar effects. In both cases, the hormonal environment promotes the kind of cell proliferation that leads to skin tag formation. Some skin tags that appear during pregnancy shrink or fall off after delivery, though many persist.
Genetics Play a Role
If your parents or siblings have skin tags, you’re more likely to develop them too. Researchers have identified specific genetic variants in a gene called CDH1 that appear more frequently in people with skin tags compared to those without. These variants may contribute to skin tag formation by affecting how cells transition between different types, a process that can encourage abnormal tissue growth. The genetic link helps explain why some people develop dozens of skin tags while others with similar body types and lifestyles develop none.
A Possible Viral Connection
One lesser-known factor is the human papillomavirus, or HPV. A study that tested skin tag tissue using PCR (a highly sensitive DNA detection method) found HPV types 6 and 11 in over 71% of skin tag samples. By contrast, only about 13% of normal skin samples taken from nearby areas tested positive. That’s a statistically significant difference, and it suggests these low-risk HPV strains may contribute to skin tag development in some people. Importantly, the high-risk HPV types (16 and 18, which are linked to cancer) were not found in any of the samples. This line of research is still being explored, but it adds another layer to the picture.
Age and Who Gets Them
Skin tags become increasingly common with age. They’re rare in children and start appearing more frequently after age 30, with prevalence continuing to climb through middle age and beyond. This makes sense given that the contributing factors accumulate over time: more years of friction, gradual increases in insulin resistance, weight changes, and the cumulative effects of hormonal shifts. By middle age, having at least a few skin tags is extremely common, and having them is not a sign of any serious skin condition.
Both men and women develop skin tags, though the distribution can differ slightly based on body composition and where friction occurs most. People with diabetes or prediabetes develop them at higher rates than the general population, reinforcing the metabolic connection.
Multiple Causes Working Together
For most people, skin tags aren’t caused by any single factor. A person with a genetic predisposition who also carries extra weight, experiences regular friction in skin folds, and has mildly elevated insulin levels is hitting multiple triggers simultaneously. That’s why skin tags often appear in groups and in predictable locations. The body is responding to a combination of mechanical, metabolic, and genetic signals all pointing in the same direction: overproduce skin cells in this spot.
Skin tags are benign and don’t become cancerous. They can be removed for cosmetic reasons or if they snag on clothing and become irritated, but they don’t require treatment. The more useful takeaway is what they might be telling you about your metabolic health, particularly if you’re developing many of them in a short period of time.